Abstract
ABSTRACT The cover crop straw may cause changes in the microbial activity and population, with repercussions on environmental changes and on the C and N dynamics, providing important information for the planning of adequate land use in the Cerrado. The objective of this study was to evaluate the effect of straw of cover crops on the soil microbial attributes and quality of organic matter. Experimental units consisted of 100 g of sieved soil placed in small plastic cups mixed with straw from cover plants. Treatments were distributed in a CRD, in a factorial scheme of 7 x 7 + 1, with seven types of straw, evaluated at 7, 14, 21, 28, 42, 63 and 105 days after incubation, and control without straw, with three replicates. The qCO2 ranged from 0.1 (Crotalaria spectabilis at 14 days) to 5.1% (Cajanus cajan ‘IAPAR 43’ at 42 days). The organic carbon and nitrogen reservoir are differently affected by straw of legumes and grasses on the dates. The incorporation of Brachiaria brizantha and Mucuna aterrima had a positive impact on the microbial attributes until the 21st incubation (qCO2, Cmic and Nmic), with little loss of carbon dioxide and growth of the microbial population. All the evaluated species presented a potential to be used in crop rotation systems, enabling no-tillage systems in the Cerrado of Piauí. However, it is recommended to select species according to specific purposes. Thus, the use of cover crops is an important tool for increasing the biological quality of Brazilian northeastern cerrado soils.
Highlights
The southwest region of Piauí is part of the Brazilian agricultural frontier called MATOPIBA (Maranhão, Tocantins, Piauí and Bahia), which is currently undergoing a great agricultural expansion and intensification of land use for the cultivation of grains, fibers, energy materials, perennial crops and irrigated agriculture (FONTANA et al, 2016; SOUSA et al, 2019)
Studies about changes in microbial attributes correlated with techniques for introducing cover crops capable of promoting high microbial activity and maintaining the soil cover ratio may favor the expansion of conservation systems
In the deployment of the use of cover crops within each assessment date, soil basal respiration (SBR) was observed at 7, 14 and 105 days after incubation with a lower values in the control treatment and higher values were found in the other treatments with values ranging from 66.45 (CO - Crotalaria ochroleuca) to 86.29 mg CO2 100 g-1 h-1 (CS - Crotalaria spectabilis) at 7 days; from 107.71 (BB - Brachiaria brizantha) to 133.17 mg CO2 100 g-1 h-1 (CCI Cajanus cajan ‘IAPAR 43’) at 14 days and, from 46.04 (MA - Mucuna aterrimaand CCI) to 75.18 mg CO2 100 g-1 h-1 (PG - Pennisetum glaucum) at 105 days
Summary
The southwest region of Piauí is part of the Brazilian agricultural frontier called MATOPIBA (Maranhão, Tocantins, Piauí and Bahia), which is currently undergoing a great agricultural expansion and intensification of land use for the cultivation of grains, fibers, energy materials, perennial crops and irrigated agriculture (FONTANA et al, 2016; SOUSA et al, 2019). The microbial attributes of the soil, such as carbon (Cmic) and nitrogen (Nmic) of the microbial biomass and baseline respiration are considered sensitive indicators of the changes caused by soil use and have been widely utilized in studies of the alterations or changes in the quality of soils in areas with a minimal anthropic intervention or cultivation (GUO et al, 2018; MANDAKOVIC et al, 2018; RODRÍGUEZ et al, 2018) These indicators can identify short term changes allowing strategies to be planned to mitigate problems caused in minimally disturbed or anthropized environments (BOECHAT et al, 2012; SANTOS et al, 2016). Studies about changes in microbial attributes correlated with techniques for introducing cover crops capable of promoting high microbial activity and maintaining the soil cover ratio may favor the expansion of conservation systems In this sense, the Cerrado of the Brazilian Northeast is currently a region of widely planted with grain crops, mainly soybeans. It is essential to assess the magnitude of the impacts of major practices such as cover crops in these new agricultural production scenarios
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